1. Field of the Invention
The present invention relates to an NRD guide circuit employing a nonradiative dielectric waveguide (hereinafter "NRD guide") circuit and a method of fabricating such NRD guide circuit.
2. Description of the Related Art
An NRD guide comprising dielectric strips inserted between parallel, opposed conductive plates and an NRD guide circuit using such an NRD guide are known from publications such as Japanese Patent Publication No. SHO 62-35281 and Japanese Patent Laid-Open Publication No. SHO 58-215804, Japanese Patent Laid-Open Publication No. SHO 63-185101 and Japanese Patent Laid-Open Publication No. HEI 7-94915.
Reference is made to FIGS. 10A and 10B in which the structure of a conventional FM radar module employing the NRD guide circuit is shown, and to FIG. 11 in which a conventional method for assembling the FM radar module is illustrated.
In the FM radar module 80 shown in FIGS. 10A and 10B, various kinds of circuit component parts, such as an FM signal generator 83, an isolator (circulator) 84, a non-reflective terminal circuit 85, a mixer circuit 86 and an antenna block 87, are disposed in respective predetermined positions between a pair of parallel, opposed upper and lower conductive plates 81, 82. Reference numeral 90 denotes a horn of a transmitter-receiver antenna.
The FM radar module 80 is assembled using positioning jigs in the following manner. First, positions at which to dispose component parts (a dielectric strip forming an NRD guide circuit element, an electromagnetic wave absorber, a dielectric strip line and the like) are determined using a plurality of positioning jigs 91, 92, 93 made of bronze or aluminum. Next, the component parts are placed at their respective positions with their bottom surfaces (those contacting the lower conductive plate 82) coated with a cyano adhesive. Upon solidification of the adhesive, the positioning jigs 91, 92, 93 are then removed by pulling them upwardly. Thereafter, the upper conductive plate 81 is secured thereto.
However, in such conventional method of assemblage, the adhesive will ooze out from between the component parts and stick to the positioning jigs with the result that the removing operations with respect to the positioning jigs becomes difficult to carry out. Further, since it is not possible to accurately determine the positions for the component parts via the positioning jigs with the adhesive stuck thereto, the stuck adhesive should be removed and repaired before the jigs are reused, resulting in an increased number of operations.
It is therefore an object of the present invention to provide an NRD guide circuit and a method of fabricating such NRD guide circuit, which is suited for mass producing such circuits, which does not require positioning jigs that need to be removed after fabrication of the circuits, and in which the positions for the component parts can be delimited without being restricted by the manners in which the parts are positioned.